Large Pits Research Articles

Electrochemical noise analysis to evaluate the localized anti-corrosion properties of PP/graphene oxide nanocomposite coatings

• Electrochemical noise was used to evaluate the localized corrosion of PP-based NCCs. • PP|Graft|GO = 0.1 illustrated the best localized corrosion performance. • PP|Graft|GO = 0.1 was able to re-passive and prevent the growth of large & deep pits. • In the presence of GO, the transients shift to the higher frequencies at all times. Electrochemical noise analysis was applied to evaluate the localized anti-corrosion performance of polypropylene (PP)-based nanocomposite coatings (NCC). In this regard, the NCCs were developed on mild steel from a solution containing PP, MAH-grafted PP, and different percentages of graphene oxide (GO). The coated samples were subjected to thermal tests, salt spray, and electrochemical noise (EN) analysis. Electrochemical potential and current noise (EPN & ECN) signals were evaluated to find information about localized corrosion. First, the raw signals were analyzed based on the empirical mode decomposition (EMD), then the 3D diagrams (intensity, time, and frequency) were plotted using the Hilbert transform. The results showed in the presence of GO, the transients shift to the higher frequencies at all times, which confirms more tendency to uniform corrosion instead of localized. Introducing 3 wt% of GO NPs into the coating leads to the electrochemical noise resistance increasing by 5 times (>10 8 Ω.cm 2 ), pit initiation rate decreasing, and pit radius reduction (by ∼5 times). As a result, MAH-grafted PP and GO in these NCCs can act as effective barriers against corrosive agents, especially the agents that cause pitting corrosion.

Probability of failure and factor of safety in the design of interramp angles in a large open iron ore mine

This paper shows the importance of performing probabilistic analyses in open pits, especially for mine planning, which can lead to more efficient ore extraction and meeting the acceptability criteria for safety in mine slopes. Three-dimensional stability analyses were performed to evaluate the future geometry of a large open pit for iron ore extraction in Brazil. The strength parameters of the lithologies were calibrated using ruptures in the pit walls. After determining the factors of safety (FoSs) from the calibrated parameters, probabilistic analyses were performed using the total range of values of each parameter under different field conditions to verify the reliability of the initial analysis. In this sense, it was possible to plot the probability of failure (PoF) and the FoS on the graph of slope height versus slope interramp angle (IRA) for the future pit in each lithology. IRA recommendations are made for two scenarios: (1) the best scenario: dry without ubiquitous joints and (2) the worst scenario: the water table at 10 m depth with ubiquitous joints in the most unfavourable direction. The results show that probabilistic evaluation is an important tool for establishing alert mechanisms in slopes that can be termed stable.

Microstructures, wear resistance and corrosion resistance of CoCrFeNi high entropy alloys coating on AZ91 Mg alloy prepared by cold spray

In this work, a fully dense CoCrFeNi high entropy alloys (HEAs) coating with homogeneous microstructure was successfully prepared on AZ91 alloy by cold spray. It is innovative to cross-integrate HEAs with Mg alloys using cold spray to break through the “bottleneck” of Mg alloys. The average microhardness of the coating was 5 times higher than Mg alloys. The weight loss of the coating in wear test was 2 orders of magnitude lower than Mg alloys. The Ecorr of the coating was noticeably improved to be ~ − 290 mVSCE and the icoor of the coating was significantly decreased by 4–5 orders of magnitude. The coating exhibited significantly spontaneous passivation due to the multi-layer passive film composed of FeO, Cr2O3 and NiO. The weight loss of CoCrFeNi coated AZ91 plates was below 1% after 28 days immersion. Lots of tiny micro-pits in size less than 1 µm were distributed on the corroded coating surface because the formation of large pitting pits was restricted. Unique corrosion mechanisms of the coatings were found: the repeatedly repassivation effect and the competing effect triggered by the rapid initiations of new pittings. The stable passive film and uniform microstructure of the coating resulted in the significant decrease of corrosion rate. The shielding effect of the coating can bring outstanding surface protection for Mg alloys.

Погребение среднесарматской культуры курганного могильника Песчаный IV: результаты сравнительно-типологического, радиоуглеродного и изотопного исследований

The paper addresses the results of the study of a rich Middle Sarmatian female burial (end of the 1st century BC — first half of the 1st century AD) discovered in the Sal-Manych steppe, on the border between the Rostov Oblast and Kalmykia. The funerary rite and goods are typical for elite burials of the Middle Sarmatian culture (diagonal burial in a large rectangular pit with a recess, two cast bronze cauldrons, clothes with golden elements, imported fibulae, a gem). The authors have conducted the comparative and typological analysis of chronological indicators found among the grave goods, as well as radiocarbon dating, which allowed to narrow down the chronological interval for the burial. Study of strontium (87Sr/86Sr) isotopes ratio from the buried woman’s dental enamel and background samples from the studied region have showed that the Sarmatian woman buried in the Peschany IV barrow group was of local origin. The interdisciplinary approach allowed to reconstruct the life story of the buried woman and her grave goods.

CULVERT DESIGN ANALYSIS USING HY-8 SOFTWARE TO DRAIN SURFACE RUNOFF DISCHARGE AT CV GUNUNG BATUJAJAR, WEST BANDUNG REGENCY, WEST JAVA, INDONESIA

CV Gunung Batujajar is a company engaged in the mining of industrial minerals in the form of andesite that applies an open-pit mining system (surface mining). Regarding the mining drainage system that is applied, there are still obstacles in dealing with drainage problems. The flow of rainwater in CV Gunung Batujajar generally flows in two places, to the large opening pit in the south with a percentage of 70% water flow and to the north by 30%. After further review, 30% of the water flow turned out to be flowing towards residents' housing and causing the water to overflow until it was flooded, thus disrupting the productivity of the population. Therefore, the authors conducted research related to the analysis of the drainage system using a culvert. In conducting the research, the authors took several types of data such as rainfall data for 10 years, field data on road geometry conditions, etc. With a planned rainfall value of 157.06 mm/day and a planned rainfall intensity of 54.45 mm/hour obtained the design runoff discharge is 0.35 m3/s. For the culvert design at the first outlet, a trapezoidal shape design is used with a base length of 0.225 m and a height of 0.2 m. As for the design at the second outlet, it is in the form of a trapezoid with a base length of 1.2 m and a height of 1.3 m. The second outlet is concluded to be more technically secure.

Analysis of the influence of super large area and super deep foundation pit excavation construction on surrounding subways

The shortest distance from the deep foundation pit envelope of the project to the subway station building is only 7.7 meters, and the deepest excavation depth of the foundation pit is about 24 meters. The surrounding environment of the foundation pit is complex, involving many buildings, the construction is difficult, and there is a great risk of construction safety. The effective control of the structural deformation of the existing subway station is the key to selecting the underground enclosure structure and construction process of the surrounding post-construction projects. Combined with the actual situation of the project, the three-dimensional numerical analysis method is used to analyze the impact of the construction of the foundation pit of the building on its adjacent structures in detail, and the relevant treatment measures are proposed. The research shows that the unloading effect caused by the large-scale excavation causes the soil outside the pit to move towards the inside of the pit. Under the influence of the soil deformation transfer effect, the Beiguan Station of the R1 line subway produces certain rebound, settlement and horizontal displacement, but the values of each deformation index are within the deformation control standard, the numerical analysis considering the influence of small soil strain can better reflect the influence of foundation pit excavation on the displacement, deformation and internal force of the existing structure. It can better match the actual engineering experience.

Long-term interactive corrosion between International Simple Glass and stainless steel

The interactive corrosion between stainless steel 316 (SS) and International Simple Glass (ISG) has been studied for 12 months. The samples were placed in intimate contact to create crevice corrosion conditions on SS in a 0.6 M NaCl solution with and without 142 ppm dissolved silica species enriched in 29Si. Corrosion on SS was observed with large pits located close to the crevice mouth at the end of 1 year in 0.6 M NaCl solution. The SS corrosion was also associated with the dissolution of nearby glass in a highly localized manner. When the leaching solution was saturated with silica species, the corrosion rate of SS was suppressed. However, the presence of SS enhances ISG dissolution in both conditions. The implications of the observed phenomena on the long-term storage of nuclear waste are discussed.

Reclaiming Wetlands after Oil Sands Mining in Alberta, Canada: The Changing Vegetation Regime at an Experimental Wetland

Surface mining for oil sand results in the formation of large pits that must be reclaimed. Some of these pits are backfilled with a myriad of substrates, including tailings rich in cations and anions, to form a solid surface. Experimental reclamation of the East in-pit located on the Syncrude Canada Ltd. mine lease was initiated in 2011 with Sandhill Wetland. Here, we report on monitoring (between 2015 and 2021) of Sandhill Wetland plant communities and significant environmental features, including base cations and water tables. Multivariate analyses demonstrated that the three dominant plant communities established in 2013 have continued to be dominated by the same species nine years after reclamation was initiated, but with reduced species richness. Plant communities have shifted across the wetland in response to water table changes and increases in sodium concentrations. The stoichiometry of base cations is unlike the natural wetlands of the region, and the surficial water chemistry of the wetland is unique. In response to variability in precipitation events coupled with wetland design, water tables have been highly variable, creating shifting water regimes across the wetland. Plant community responses to these shifting conditions, along with increases in base cation concentrations, especially sodium, provide background data for future in-pit reclamation designs. The plant responses underscore the need to develop reclamation designs for landscapes disturbed by mining that alleviate extreme water table fluctuation events and decrease cation concentrations to levels that approach natural wetlands.

Late Woodland feasting and social networks in the lower Missouri River region

Feasting and its function among small scale societies have received little attention among many descriptive and theoretical studies of this activity. Evidence of feasting focused on large roasting pits by Late Woodland (AD 500–1000) hunter-gatherer-gardeners in the lower Missouri River region on the eastern edge of the Great Plains is presented. Two features at the Quixote site and lipid analyses of stones from them attest single events focused on roasting deer and fish, and perhaps ritual use of red cedar and ceramic pipes. Such features at other Late Woodland sites in the LMRR, specifically the Valley Falls locality of the Delaware River valley in northeastern Kansas, are reinterpreted. Burned stone features at Middle Woodland sites differ and suggest pit roasting was a practice of dispersed Late Woodland groups. Feasting for solidarity forged a social network based on reciprocity, not competition, to mitigate food insecurity among diffuse, low level food producers.

Observation of threading dislocations with a c + m type Burgers vector in HVPE GaN substrates using multi-photon excitation photoluminescence and TEM

Dislocations that have a large Burgers vector are potential leakage current pathways in power devices. In this study, we analyzed the dislocations under a large pit (L-pit) produced by chemical etching in a hydride-vapor-phase-epitaxy GaN substrate by using multi-photon excitation photoluminescence (MPPL) and transmission electron microscopy (TEM). Three-dimensional dislocation images reconstructed from MPPL clearly showed that two threading dislocations (TD-1 and TD-2) approached each other laterally while propagating along the growth direction [0001]. They interacted near the sample surface and merged into a single dislocation whose large Burgers vector was responsible for the L-pit formation. A TEM observation operated in large-angle convergent-beam electron diffraction mode unambiguously identified the Burgers vectors of the two dislocations as bTD-1=13[2-1-1-3] (c + a type) and bTD-2 = [10–1–1] (c + m type). The c + m type is extremely rare in GaN. The merged dislocation appeared to constitute Burgers vectors of all three components of c, m, and a.

Fractal dimensions of hydraulic parameters in sand mined alluvial channel

Abstract Long-term extraction of sand from a river causes large mining pit on the river bed, and these pits change their fluvial processes. In this paper, an experimental study is executed to interpret the turbulence flow structure in a mining pit. This research mainly focuses on the fractal dimension of velocity fluctuations and Reynolds shear stress (RSS) of flow in the longitudinal and vertical plane for a mining pit region. The results show that the magnitude of fractal dimension for velocity fluctuation and RSS is smaller in the mining pit than the upstream and downstream of the pit. The large values of fractal dimensions at the pit downstream show an increase in flow roughness. It is found that the Taylor microscale decreases towards the channel bed, and this is because of increasing turbulence dissipation near the bed region. We have observed a significantly lower value of Taylor microscale in the mining pit. The higher value of the Taylor microscale is found far downstream of the pit. Nondimensional turbulence mixing length shows a decrease in the traversing length of an eddy at the far downstream of the pit.

Novel insights into prehistoric land use at Stonehenge by combining electromagnetic and invasive methods with a semi-automated interpretation scheme

Geophysical survey methods have led to high-resolution mapping of subsurface remnants of ancient landscapes at continually expanding spatial scales. Yet, particularly when applied across entire archaeological landscapes, spanning hundreds of hectares, resultant datasets provide little direct information about inhabitation, environments or change over time.Focusing on a 2.5 km2 area around Stonehenge, we show how geophysical soil survey, when combined with targeted sampling and excavation, can enable reliable empirically-grounded identification of complex activity traces. Particular focus lies on anthropogenic dug pits, identification and interpretation of which are vital in European earlier prehistoric archaeology due to their close connection with inhabitation and ceremonial practices. By integrating frequency domain electromagnetic and invasive datasets, and using a semi-automated interpretation scheme, we identified previously unknown concentrations of large pits (with diameters >2.4 m) among several thousand smaller pits and natural features across the Stonehenge landscape. Excavations of a subset of identified features demonstrate that, in this area, our investigative methodology is 66% accurate for identifying large anthropogenic pits. Our results have significant implications for understanding Stonehenge and its landscape setting, revealing elusive forms of Mesolithic to later Bronze Age land use that - even within the world's most intensively researched archaeological landscape - have gone unrecognized until now.These findings underscore both the crucial role of archaeological excavation as an essential basis for reliable interpretation of geophysical data, as well as the perils of inductive visual interpretation of features’ morphologies and their spatial configuration in non-invasive survey data.

Numerical Study on the Effect of Large Deep Foundation Excavation on Underlying Complex Intersecting Tunnels

The effect of large deep foundation excavations on the surrounding existing tunnels is a problem that cannot be avoided in the current construction background. This effect is difficult to assess precisely, especially when the geometry of the tunnels and pits is complex. In this paper, a three-dimensional (3D) finite element model has been developed based on a case containing four complex intersecting tunnels and a large deep foundation pit. The model used the hardening soil model with small-strain stiffness (HSS) and the Hoek–Brown (HB) model to describe the mechanical properties of the soil and rock, and various methods including the standard penetration test (SPT) and heavy dynamic penetration test (HDPT) were used to determine the model parameters. The results of the analysis are as follows: the excavation of the foundation pit caused the tunnels to heave and the heave deformation conforms to the normal distribution; the maximum heave of numerical simulation is 3.1 mm which is consistent with the field data; the horizontal displacement, horizontal convergence, and vertical convergence of the tunnels caused by the excavation of the pits are small, and all kinds of deformations meet the control requirements; the intersection of multiple tunnels shows obvious stress concentration when the tunnels were constructed, and the lining stress slightly decreases as excavation progresses.

ABYLAI SETTLEMENT — SITE OF THE EARLY IRON AGE IN CENTRAL KAZAKHSTAN

The Abylai settlement was discovered by the author in 2006, and in 2016 the excavations of this site began. This settlement is located in the Karkaralinsky district of the Karaganda region of the Republic of Kazakhstan. In 2016-2021 six field campaigns headed by the author were carried out, the total area of which is more than 1200 m2 (fig. 1). The materials of the 2020 excavation, as well as the overview of the main multidisciplinary studies are published in the paper.
 Excavation area 5 was 185.5 m2. In this area, the remains of five structures with stone foundation walls, as well as household pits were discovered (fig. 2, 3). One pit has large dimensions: 5.9 × 3.45 m along the top, 5.3 × 2.9 m along the bottom (fig. 4). It was filled with three layers of ash and the soil mixed with ash. Perhaps this pit was used to drain the rain and melt water. The burial (fig. 5, 6), which does not belong to the inhabitants of this culture, was found in the excavation area. Such burials belong to the «Korgantas type» and date to the 4th—5th centuries BC.
 Fragments of ceramics (fig. 7), numerous stone tools (fig. 8), among which there are objects for grinding grains and other plant residues, hoes, graters, etc., were found in the excavation area.
 Materials, found in 2020, supplement the information previously received about this site. A large amount of data has now been accumulated. In this regard, the complex of multidisciplinary studies has been launched in recent years. Archaeozoological and traceological analyzes have yielded important results. Based on more than 11,000 animal bones found at the settlement, the composition of the herd, having consisted of sheeps, cows and horses was ascertained. A more important result is the determination of the slaughter season: it turned out that the entire mass of livestock was slaughtered in the period from late autumn to early spring. This conclusion proves the author’s hypothesis about the winter character of such settlements. Part of the bones (over 6000) was found in a large pit measuring 8 × 4 × 0.9 m. These were the bones of sheep and cows, thrown into the pit and covered with ashes. Analyzes showed that all the bones were thrown into the pit at the same time and belong to animals that died in the early spring. This fact is the first case in Kazakhstan of finding the remains of animals that died as a result of spring starvation or epizootic. The entire results of the archaeozoological analysis are now preparing for publication.
 More than 500 stone tools were found at the site of Abylai. In 2020, 150 items were subjected to trace analysis, as a result of which the functions of 139 tools were determined. Of these, 130 turned out to be tools that were intensively used in various cases: earthworks, vegetation processing, work with livestock products, as well as the processing of metal surfaces (whetstones). Moreover, all bars have traces of iron objects (Beisenov, Gorashchuk, Duysenbay 2021). In 2021, a new group of stone tools was covered by traceological analysis. Out of 250 items, 202 had a function determined. Thus, there is a good prospect to study the economic structures of the Abylai settlement. The few grains of cultivated cereals found by carpological analysis, including millet, barley (fig. 9) and wheat, provide additional information about the life of the ancient inhabitants of the settlement.
 The Abylai settlement, like other sites of the Tasmola culture, dates back to the period of the 8th—5th centuries BC (Beisenov et al. 2016; Beisenov 2017). Terminus ante quem of the settlement is additionally confirmed by the burials of the Korgantas time. These burials are dated within the period of the 4th—2nd centuries BC. The presence of them proves that closer to the 4th century BC the Abylai settlement had already been abandoned. A more accurate dating of the settlements of the Saka Age of Central Kazakhstan should be expected in future studies.

Damage behaviors of silica microparticles on fused silica optics under 355 nm high fluence laser

Particulate contaminants are common damage precursors on optics in the daily operation of high laser power systems. In this paper, the damage behaviors of silica particles attached to the front and back surfaces of fused silica optics under the irradiation of a 355 nm laser were studied. Results showed that silica particles on the front surface tend to splash severely under high fluence, while the particle on the back surface forms a large laser-induced shallow pit (LSP)-like pit on the substrate. Different damage morphologies were observed, and damage mechanisms were also proposed.

Deformation Control of Subway Stations under the Influence of the Construction of Deep and Large Foundation Pits with Composite Support Systems

The excavation depth of a deep and large foundation pit of a composite support system is 25.5 m, the minimum clear distance from the main structure of the station is 10.6 m and the closest distance to the entrance and exit structure is only 3.6 m. Relying on this project, numerical simulation, field monitoring and other methods are used to study the deformation law of the self-supporting system, the ground settlement and the subway station under construction. Then, the influence of different support parameters on the deformation of the subway station and track is analyzed, and the internal relationship between the deformation value of the station and track and the support parameters is further discussed. The main work and achievements are as follows: (1) Through field measurement and analysis, the deformation history of the station and track in the excavation is studied. The obtained results show that the interbracing + pile–anchor composite support structure has better control over the deformation of adjacent stations and tracks. Comparing the simulated value of station and track deformation with the measured data, it is concluded that the simulated and measured deformation trends remain consistent, and the maximum deformation value corresponds to the middle position of the foundation pit. This confirms the rationality and reliability of the composite support system model. (2) The analysis of the influence of different support parameters on the maximum deformation value of the subway station and track shows that the deformation of the station and track is less affected by the pile diameter of the retaining pile and the size of the interbracing section. It is greatly affected by the embedding depth of the retaining pile and the number of support channels. It is suggested that the optimal parameters should be a pile diameter of 1.0 m, embedding depth of 8 m, four interbracings and an interbracing section of 1.0 m × 1.0 m.

Study on immersion corrosion behavior and mechanism of SDCM die steel for hot stamping

Adopted immersion method to systematically study the corrosion behavior of SDCM steel for hot stamping. For specimens with the same hardness of 54 HRC, the corrosion resistance of 1030 °C quenched samples were better than that of 1060 °C quenched samples. After 1030 °C quenched, the hardness was adjusted to 50 HRC, 52 HRC and 54 HRC by tempering process, and then applied 50 MPa tensile stress to these three kinds of hardness samples. With the increase of hardness, the corrosion area decreased from 21.82% to 13.47%, and the number of large pits decreased from 27 to 7 on the area of 40 mm2. Stress has an important effect on corrosion. When the loading stress was less than 100 MPa, the corrosion area/pitting numbers increased with the increase of stress, but the aspect ratio decreased, and the decreasing range was large. When the loading stress was more than 100 MPa, the corrosion area/pitting number decreased with the increase of stress, the aspect ratio also decreased, but the decreasing range was smooth, which was mainly related to the concentration of adsorbed dissolved oxygen; finally, we discussed the initiation and growth behavior of pitting pits and then schematically described its model.

Anthropogenic fire fingerprints in Late Pleistocene and Holocene sediments of Sodmein Cave, Egypt

Sodmein Cave in Egypt is an exceptional archive for the study of past human behavior and anthropogenic fire history. Stratified remains of human occupation were excavated, ranging from the Middle Stone Age to the Neolithic. Hearths were repeatedly detected throughout the stratigraphy, with the lowest Pleistocene level having particularly large fire pits. This study is the first to apply a black carbon (BC) method on sediments bearing archaeology from the last 120,000 years. The method oxidizes BC to benzene polycarboxylic acids (BPCA) as a proxy for fire residue input. We detected significant changes in BC amounts throughout the stratigraphy; the highest contents in the form of two distinctive peaks were found in samples corresponding to the beginning of the Late Pleistocene (3.3 and 2.2 g BC kg−1, respectively), indicating frequent burning. In the overlying layers, BC remained low (on average: 0.2 g BC kg−1) until the beginning of the Holocene, when contents increased, and human influence became visible again (1.7 g BC kg−1). Also, BPCA composition as a proxy for changes in fire temperature changed significantly over the stratigraphy. In the Pleistocene, residues of hotter fires were predominantly found, while the Holocene was characterised by a change to low-temperature fires. Variations in BC input and source are in agreement with the archaeological results, demonstrating the varying intensities and recurrence of human visits to the shelter during the last 120,000 years, but also show the potential to resolve different phases of human occupation more finely, when the archaeological findings are accompanied by geochemical BC analyses.

Особенности формирования поселенческой структуры верхнепалеолитической стоянки Юдиново по материалам археологических и геохимических исследований 2015—2018 гг.

This article presents the results of recent archaeological and geochemical studies at the Late Palaeolithic site of Yudinivo. The reported research was focused on the area with dwelling No. 5, a large pit with mammoth bones on its bottom and an ash damp. The micro-stratigraphy of the cultural layer makes it possible to identify a number of stages in the life history of large household constructions. It has been established that an ash damp was formed first, while dwelling of mammoth bones was erected somewhat later and simultaneously a large pit was dug with large mammoth bones laid on its bottom. The pit and the dwelling appear to have been constructed at the same time and used synchronously with the ash damp. The geochemical analysis of the deposits above the ash damp and the pit, as well as in the filling of the latter, show that the cultural layer formed during an extremely long period of time with long intervals. One can distinguish at least four episodes corresponding to different climatic conditions. Two of these episodes are characterized by a high anthropogenic load, indicating that the site occupation was particularly active 17100—15000 cal. BP and 14000—13200 cal. BP.

Numerical Simulation Study on Construction Effect of Top‐Down Construction Method of Suspended Diaphragm Wall for Deep and Large Foundation Pit in Complex Stratum

In order to study the deformation of a diaphragm wall and the settlement of surrounding soil under the complicated conditions of the deep and soft soil layer, which is underlying inclined rock and top‐down construction method, the construction scheme of suspended diaphragm wall based on the engineering practice of Oujiang North Estuary deep and large foundation pit of Wenzhou S2 railway is proposed, and the research method of numerical simulation is adopted in this article. By using Midas GTS finite element software, a three‐dimensional model of deep and large foundation pit excavation with top‐down construction method is established, and the internal force, deformation, and surface settlement of surrounding soil of suspended diaphragm wall with different depths into rock (1 m, 2 m, and 4 m) are analyzed. Furthermore, the optimization simulation research on the anchor locking scheme is carried out for the determined footed diaphragm wall. Similarly, the anchor locking scheme at a depth of 1 m into the interface between soil and rock is selected as the supporting scheme of the footed diaphragm wall through the simulation results. The research results of this article can guarantee the safety of diaphragm wall construction of deep and large foundation pit in complex stratum.